Upon a little bit of experimentation, I can see that your option does appear quite flexible, and could probably do the job with at little tweaking. In my younger years, I took the habit of using a child's primer pencil to mark time signatures on difficult scores.
While the example you've shown is considerably larger and easier to read, I'm concerned that it would really interfere with the rest of the score layout. This is indeed an improvement, but the convention as I've seen it (and as shown in the example posed by the OP) is to have the time signature span several staves - usually covering entire instrument families.
